<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>Canvas烟花</title>
    <meta name="description" content="">
    <meta name="keywords" content="">
    <link href="" rel="stylesheet">
    <style type="text/css">
        body {
            padding: 0;
            margin: 0;
            background: #000;
        }
    </style>
</head>

<body>
    <canvas id="canvas">Canvas is not supported in your browser.</canvas>
    <script type="text/javascript">
        window.requestAnimationFrame = (function () {
            return window.requestAnimationFrame ||
                window.webkitRequestAnimationFrame ||
                window.mozRequestAnimationFrame ||
                function (callback) {
                    window.setTimeout(callback, 1000 / 60);
                }
        })();

        var canvas = document.getElementById("canvas"),
            ctx = canvas.getContext("2d"),
            cw = window.innerWidth,
            ch = window.innerHeight,
            fireworks = [],
            particles = [],
            hue = 120,
            timerTotal = 80,
            timerTick = 0;

        canvas.width = cw;
        canvas.height = ch;


        function random(min, max) {
            return Math.random() * (max - min) + min;
        }

        function caculateDistance(sx, sy, tx, ty) {
            var xDistance = sx - tx,
                yDistance = sy - ty;
            return Math.sqrt(Math.pow(xDistance, 2) + Math.pow(yDistance, 2));
        }

        function Firework(sx, sy, tx, ty) {
            this.x = sx;
            this.y = sy;
            this.sx = sx;
            this.sy = sy;
            this.tx = tx;
            this.ty = ty;
            this.distanceToTarget = caculateDistance(sx, sy, tx, ty);
            this.distanceTraveled = 0;
            this.coordinates = [];
            this.coordinatesCount = 3;
            while (this.coordinatesCount--) {
                this.coordinates.push([this.x, this.y]);
            }
            this.angle = Math.atan2(ty - sy, tx - sx);
            this.speed = 2;
            this.acceleration = 1.05
            this.brightness = random(50, 70);
            this.targetRadius = 1;
        }

        Firework.prototype.update = function (index) {
            this.coordinates.pop();
            this.coordinates.unshift([this.x, this.y]);

            if (this.targetRadius < 8) {
                this.targetRadius += 0.3;
            } else {
                this.targetRadius = 1;
            }
            this.speed *= this.acceleration;
            var vx = Math.cos(this.angle) * this.speed,
                vy = Math.sin(this.angle) * this.speed;
            this.distanceTraveled = caculateDistance(this.sx, this.sy, this.x + vx, this.y + vy);
            if (this.distanceTraveled >= this.distanceToTarget) {
                createParticles(this.tx, this.ty);
                fireworks.splice(index, 1);
            } else {
                this.x += vx;
                this.y += vy;
            }
        }

        Firework.prototype.draw = function () {

            ctx.beginPath();
            ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length -
                1][1]);
            ctx.lineTo(this.x, this.y);
            ctx.strokeStyle = 'hsl(' + hue + ',100%,' + this.brightness + '%)';
            ctx.stroke();

            ctx.beginPath();
            ctx.arc(this.tx, this.ty, this.targetRadius, 0, Math.PI * 2);
            ctx.stroke();
        }

        function Particle(x, y) {
            this.x = x;
            this.y = y;
            this.coordinates = [];
            this.coordinatesCount = 5;
            while (this.coordinatesCount--) {
                this.coordinates.push([this.x, this.y]);
            }
            this.angle = random(0, 2 * Math.PI);
            this.speed = random(1, 10);
            this.friction = 0.95
            this.gravity = 1;
            this.hue = random(hue - 20, hue + 20);
            this.brightness = random(50, 80);
            this.alpha = 1;
            this.decay = random(0.015, 0.03);
        }

        Particle.prototype.update = function (index) {
            this.coordinates.pop();
            this.coordinates.unshift([this.x, this.y]);
            this.speed *= this.friction;
            this.x += Math.cos(this.angle) * this.speed;
            this.y += Math.sin(this.angle) * this.speed + this.gravity;
            this.alpha -= this.decay;
            if (this.alpha <= this.decay) {
                particles.splice(index, 1);
            }
        }

        Particle.prototype.draw = function () {
            ctx.beginPath();
            ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length -
                1][1]);
            ctx.lineTo(this.x, this.y);
            ctx.strokeStyle = 'hsla(' + this.hue + ',100%,' + this.brightness + '%,' + this.alpha + ')';
            ctx.stroke();
        }

        function createParticles(x, y) {
            var particleCount = 30;
            while (particleCount--) {
                particles.push(new Particle(x, y));
            }
        }

        function loop() {
            requestAnimationFrame(loop);
            hue += 0.5;
            ctx.globalCompositeOperation = 'destination-out';
            ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
            ctx.fillRect(0, 0, cw, ch);
            ctx.globalCompositeOperation = 'lighter';
            var i = fireworks.length;
            while (i--) {
                fireworks[i].draw();
                fireworks[i].update(i);
            }
            var i = particles.length;
            while (i--) {
                particles[i].draw();
                particles[i].update(i);
            }
            if (timerTick >= timerTotal) {
                fireworks.push(new Firework(cw / 2, ch, random(0, cw), random(0, ch / 2)));
                timerTick = 0;
            } else {
                timerTick++;
            }
        }
        window.onload = loop;
    </script>
</body>

</html>